Dry concentrator



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' DRY CONCENTRATOR Filed March 2, 1936 5 Sheets-Sheet 4 @Lav IN 'a m T- l f/w//vroe CLASSIFYING. SEP/mme, @m33 Marenga L Assomm@ somos Jan. 24, 1939. H ,1.\- ADAMS 2,144,671

i DRY CONCENTRA'ROR Filed March 2, 1936 5 Sheets-Sheet 5 Patented Jan. 24, 1939 UNITED vs'mxriazs `rn'rrivi OFFICE 6 Claims.

Myinvention relates to the art of separating granular or pulverized material, and has its greatest utility in the concentration of ores so as to remove the valuable constituents from the remaining mass of materials forming a body of ore.

The use of ore concentrators is extensive, and devices for ore concentration have been devised for-handling the ore in wet form and also in dry form. Wet concentrators have been developed to 10 a high state of eiciency, but it is believed that the,.dry concentrators now obtainable have relatively low eiiiciency. 'I'here are many deposits of valuable minerals in locations where water is extremely scarce or unobtainable at a cost warl5 ranting its use in wet concentration. It is an object of my invention to provide a dry concentrator which may be used under the conditions above set forth, owing to the fact that it does not require a wet ore mixture in its operation, and

which is of such high e'ciency and simplicity that it may be profitably employed.

It is an object of theinvention' to 'provide a dry concentrator which maybe operated at low cost, and-which, due to its'low loss-of -valuable materials, is especially suited for use on ores of low value. This does not mean, however, that the concentrator may not "be advantageously used for concentration of Ahigh value ores, for the high eiiiciency o`f the device is maintained regardless of the 'assay of the ore.

It is an object of the invention to provide a dry concentrator which 'may be satisfactorily used on ores ground to larger size than is ordinarily maintained in concentrating practices.

It is an object of the invention to provide a concentrator which will deliver a concentrate having a'minimum of Waste materials therein.

It is an object of the invention to provide a concentrator having a wall member so formed 40 that air may pass therethrough, this'wall member being in the form of a loop or continuous belt, and being supported so'that it may pass continuously through an upwardly sloping path of movement. In a concentrator of this character, the

invention has for additional objects to provide a perforate wall construction on which the concentration functions may be performed, this wall being of novel form and contributing directly to the valuable results obtained; to provide a simple and effective means for forming concentrate receptacles or pockets on the upper face ofthe wall member,e such concentrate receptacles or pockets having a simple guard means associated therewith; to provide a novel and controllable means for feeding the ore tothe f :oncentrator wherein a blast of air is employed to distribute the ore particles rearwardly across the face of the wall member; to provide a simple means for controlling the aforesaid blast of air so that, in addition to its previously stated valuable util- 5 ity, the blast of air or portions thereof will clean the upper surface of the wall member, thereby removing fine Waste materials; to provide a simple means for causing a. breathing of air through the wall member; to provide a means for con- 10` trolling the vertical movement of the wall member during the operation of concentration; to provide an e'icient feeder for feeding the granulated or pulverized ore to the concentrator, wherein a roll member having a spiral groove is 15 employed; and to provide means whereby the feeding of the concentrate, the velocity of the wall member, and the breathing action of air through the wall member may be independently controlled or regulated in accordance with the 20 characteristics of the ore being treated so as to at all times maintain a high elciency in the operation of the concentrator.

Further objects and advantages of the invention will be brought out in the following part of 25 the specification.

Referring to the drawings, which are for illustrative purposes only,

Fig. 1 is a right-hand side View of a preferred Y embodiment of my invention. 30

Fig. 2 is a partly sectioned plan view corre sponding to Fig. 1.

Fig. 3 is a left-hand side view of the device.

Fig. 4 is a partly sectioned rear end view of the device. 35

Fig. 5 is an enlarged section on a plane represented by the line 5-5 of Fig. 4.

Fig. 6 is a fragmentary section taken as indicated by the arrow 6 of Fig. 5.

Fig.'7is an enlarged fragmentary section taken 40 as indicated by the line 'I-l of Fig. 5.

Fig. 8 is an enlarged fragmentary plan view corresponding to Fig. 7.

Fig. 9 is an enlarged fragmentary sectional view clearly showing the construction of the 45 wall member and the manner in which concentrate pockets are formed along the edges of the riflle bars.

In the preferred form of the invention shown, I provide a wall member 20 which is made in the 50 form of a continuous loop or belt, so that a portion thereof may be continuously moved through a sloping path during the operation of the concentrator. This wall member, as shown in Fig. 9, comprises a perforate supporting member 2| Acon- 5g sisting of a wire mesh screen, and a layer of finely woven fabric 22, such fabric being preferably airplane linen. The fabric 22 lies on the upper or outer surface of the screen 2| and is secured thereto by means of laterally directed riiiie bars 23 which are spaced apart in substantially the manner shown so that areas 24 of the fabric 22 are left exposed between the riiile bars 23.

The riie bars 23 are secured in place by means of small bolts 25 which pass through openings in the bars 23, the fabric 22, and the screen 2|, and also pass through guard strips 26 which rest against the under face of the screen 2|. The bolts 25 are spaced relatively close together and are tightened just sufficiently to secure the fabric 22 without causing the same to pucker. As best shown in Figs. 7 and 8, edge strips 21, of ribbon steel, are secured to the edges of the screen 2| in such a manner that the edges of the screen 2| overlap the edges of the strips 21. Side walls or guards for the areas 24 are formed by strips 28 of leather or other exible material, these strips being secured in place by means of screws 29. The edge strips 21 reinforce the edges of the Wall member 2|), and the bars 23 and the guard strips 26 provide the wall member 20 with lateral sti'ness.

To support the wall member 20 in operative position, I provide a sloping member 3| which is essentially a frame comprised of side bars or channels 32 held in spaced relation by cross bars 33 which are preferably structural angles. The side bars 32 slope upwardly, and near the upper ends thereof bearings 34, which are secured to the under edges of the side bars 32, support a shaft 35 carrying a pair of sprockets 36 having teeth 31 for engaging sprocket holes 38 in the edge strips 21 of the wall member 20. Near the lower ends of the side bars 32, bearing members 39, secured to the under faces of the side bars 32, support a shaft 4| which carries a pair of idler wheels 42.- The wall member 20 in its continuous belt-like form is run over the sprocket wheels 36 and the idlers 42 which are laterally spaced so as to engage the ribbon steel edge strips 21 of the wall member 20. Each of the side bars 32 is supported by front and rear posts 43 and 44, which may be connected by reinforcing channels 45 and may have their lower ends connecting to channels 46 forming footings for the concentrator.

As best shown in Figs. '1 and 8, the upper part of the wall member 28, between the sprocket wheels 36 and the idlers 42, has its edges supported on strips 41 which may be formed of wood and which provide shoulders 48 on which the outer edge portions of the edge strips 21 may slide. Sealing strips 49 of suitable yieldable material, such as rubber or rubberized fabric, are supported adjacent and within the shoulders 48 by means of strips 5|.which are secured to the inner faces of the strips 41. Hold-down strips 52 are mounted so as to yieldably force the edge strips 21 downwardly against the shoulders 48 and against the sealing means 49. Such holddown strips 52 may be made of hard wood with longitudinal grooves 53 formed in the lower faces thereof, with a view to reducing the area of engagement with the upper faces of the strips 21. The hold-down strips 52 have openings 54 in the upper faces thereof in which springs 55 are retained. Adjusting screws 56 threaded through the cross bars 33 have their lower ends projecting into the upper ends of the openings 54 so as to bear downwardly against the springs 55. To

prevent granular or pulverized materials from working under the hold-down strips 52, guard strips, or sealing strips 51, of flexible material, such as leather or rubber, are secured to the inner faces of the members 52 by means of screws 58, and in such position these sealing strips 51 engage the upper faces of the edge strips 21 adjacent the outer edges of the guard members 28.

Under the cross bars 33 and below the upper portion of the wall member 20, lateral supporting bars 59 are extended between the strips 5|, these bars 59 being held by clips 6|, as best shown in Fig. '1. By means of longitudinal angles 62 which are bolted to the lateral members 59, lower supporting strips 63 are secured in such position that the guard strips 26 of the wall member 20 will ride thereon as the wall member 20 moves from the idlers 42 to the sprocket wheels 36. These strips 63 are relatively rigid so that downward movement of the wall member 20 is substantially prevented. The wall member 20 is held resiliently downwardly against the strips 63 by means of arched leaf springs 64 which engage the lower edges of intermediate hold-down strips 65 which are secured above the wall member 28 in longitudinal relation to the frame member 3|: by means of longitudinal angles 66 which are bolted to the cross members 33, as indicated at 61. The ends of the arched leaf springs 64 are secured to the upper faces of the riffle bars 23 by means of screws 68 disposed intermediate the bolts 25 by which the bars 23 are held in place.

I provide a feeder 69 for feeding granulated or pulverized materials to the upper face of the wall member 20. this feeder 69 including a hopper 1| of a length corresponding substantially to the width of the exposed fabric 22. This hopper 1| may be supported on legs 12 and 13 which are connected to the side bars 32. As shown in Fig.'5. the hopper 1| has downwardly converging side walls 14 and 15 disposed so as to form an opening 16 between the lower ends thereof. this opening 1B being substantially closed. or nearly so, by a feed roll 11 secured to an axle 18 supported by bearings 19 and having a gear 8| thereon through which the shaft 18 and the feed roll 11 may be rotated in the direction indicated by an arrow 82 in Fig. 5. The feed roll 11 has a spiral groove 83 running from end to end thereof. which spiral groove, as the surface of the roll 11 exposed in the opening 15 of the hopper moves downwardly, tends to move the material in the extreme lower part of the hopper 1| laterally. thereby straightening any elongated or sliver-like particles so that they may pass downwardly through the small discharge space 84 formed between the periphery of the roll 11 and adjustable plates 85 which are supported at the lower edge of the wall 15 These plates or gate members 85 have the upper edges 86 thereof bent forwardly so that thev may be en gaged bv adiusting screws 81 which are threaded through a supporting member 88 consisting preferably of structural angle secured to the wall 15 in spaced relation so that the gate members 85 may slide in the space between the wall 15 and the member 88 under control of the adjusting screws 81 so as to control the width of the feed opening 84.

The invention also provides a means for producing a blast of air traveling downwardly under the feeder 69. as indicated by arrows 89 in Fig. 5, this blast of air being so proportioned relative to the character of the materials being fed from the hopper 1| that the materials will be discharged or conveyed along. the plane parallel to the upper face of the wall member 20 as indicated in general by arrows 9|. Accordingly, the ore is not dropped directly from the hopper 69 in the surfaceof the wall member 20, but is spread downwardly therealong in the form of a veil or heavily charged moving atmosphere from which the particles of ore drop onto the upper surface of the wall member 20. This characteristic manner of feeding the ore particles to the wall member 20 I consider of supreme importance in conjunction with other features herein disclosed, in producing improved results in concentration. I have found that at times I have obtained an efficiency of concentration of 97% and have conducted numerous runs in which the vefliciency has been 93%. By eiciency of concentration I mean the actual quantity of valuable constituents removed from the cre as compared with the entire quantity of valuable constituents in the ore, as determined by assaying the ore.

The means for producing the blast of air referred to in the preceding paragraph is in the form of a blower 92 which is secured to the upper ends of the side members 32 and has a discharge mouth 93 which is nearly as wide as the wall member 20 and is of relatively small vertical dimension. The discharge end of the member 93 is disposed near the upper surface of the wall member 20 and above or leftwardly of the feeder |39. The air blast producing means, or blower 92, is provided with a controllable means for creating a flow of air downwardly against the upper face of the wall member 20 after such wall member has passed upwardly under the feeder 69. As best shown in Fig. 9, this control means consists of a plate or vane 94 mounted on a lateral shaft so that it may be swung downwardly from the dotted line position thereof indicated at 96 to such position, as indicated by full lines, that it will cause a downward deflection of air,

as indicated by an arrow 91, against the upper face of the fabric 22 so as to remove light waste materials from the surface of the fabric, to prevent such waste materials from being carried on over into the concentrate receiver which consists of a sloping wall 98, Fig. 5, disposed below the lower extension S9 of the wall member 20, and a removable receptacle |0| disposed at the lower end of the wall member 98 so that the concentrates may collect therein. The sprocket wheels 35 turn in the direction of arrows |02 during the,

operation of the concentrator. As the Wall member 20 passes over the sprockets 35 in the direction indicated by the arrows |02, the concentrates drop from the wall member 20 onto the sloping wall 98 and subsequently move down this wall 98 to the receptacle |0|.

I'conjunction with the parts previously described, I provide a means for producing a breathing of air through that portion of the wall member 20 which is traveling upwardly from the idler wheels 42 to a roller |03 disposed near the sprocket wheels 30, as best shown in Fig. 5. A chamber |04 is produced adjacent the under face of ,the foregoing part of the wall member 20. The sides of this chamber |04 are formed by the strips 5| and by metal walls |05 which extend -downwardly from the strips 5|, as best shown in Fig. 5. These walls |05 fit close to the idler wheels 42, and the lower ends of the upper edges of the plates or walls |05 are curved as indicated at |06. Between the lower ends of the walls |05, a roller |01 is supported on a shaft |08, this roller |01 engaging the innerface of the wall member 20 in a plane substantially horizontal with the axis of the shaft 4| carrying the idler wheels 42. Between the lower edges of the metal walls |05, metal' walls |09-, and ||2 are extended. The walls and ||2 are disposed in V-shaped arrangement so as to pass around the shaft 4|, and at the lower edge of the wall a door ||3 may be provided through which collected materials may be periodically withdrawn. To permit leakage of air outwardly from the chamber |04 along the shaft'4l, a tube ||4 is placed around the shaft 4|, this tube extending from one wall |05 to the other. I

At the upper edge of the wall |09 of th chamber |04, a bellows means ||5 is situated, this bellows means including a rectangular frame ||6 comprised of lateral channels ||1 and ||8 secured by means of bolts ||9 to` the side niembers 32, and longitudinal channel members |'2|. By hinges |22 connected to the lateral member ||1, a plate |23 is secured within the frame H6, The plate |23 has air openings |24 therethrough equipped with flap valves |25 which are securedto the upper face of the plate |23. Means are provided for vertically swinging the plate |23 so as to produce a periodic upward pumping of air into the chamber |04, a portion of this air passing through the wall member 20 and assisting in the concentrating action, as will be hereinafter described. The operating means for the plate |23 includes a laterally extending shaft |26 having levers |21 xed thereon, these levers being connected to the upper end of the plate |23 by means of links |28. For rocking the shaft |26, so as toin turn swing the levers |21, an adjustable crank or lever |29 is xed on the rightward end of the shaft |26, as shown in Fig. l. This member 29 includes a body |3| which is connected to the end of the shaft and has a lateral opening |30 for a screw |32 provided with a clevis |33 or other suitable pivot means at its lower end. This screw |32 may be raised or lowered by turning flat nuts |34 and |35 which are threaded on the screw |32 so as to engage the ends of the body |3|. By means of a connecting rod |36 containing a turn buckle |31, the clevis |33 of the screw |32 is connected with an eccentric |38 mounted on the rightward end of a shaft 39 supportedI across the rear of the post 44. As best shown in Fig. 7, the edges of the bellows plate |23 are provided with projecting rubber strips |4| which engage the inner faces of the channels ||8 and |2| and form sealing means for limiting the leakage of air around the edges of the plate |23 during the operation thereof. To drive the concentrator, a motor |42 is shown in Fig. 2 adjacent the rear end of the concentrator, this motor |42 being connected to a short jack shaft |43 carrying a drive sprocket |44 and a pulley |45. The sprocket |44 drives the shaft |39 through a chain |46 which extends over a sprocket |41 which is fixed to the shaft |39. 'I'he pulley |45 is connected with a pulley |48 on the shaft |49 of the blower 92 by a belt |5|. This direct connection with the motor results in driving the blower 92 at relatively high speed. On the leftward end of the shaft |39 is a pulley |52 which is connected by means of a belt |53 with a pulley |54 mounted on a laterally extending shaft |55 carried by bearing members |56 which are mounted on the legs 13 of the feeder 69. Brushes |51 of circular form are secured to the shaft |55 in positions to engage the upper faces of the guard strips 28 and the inner edges 28a. of the metal-edged strips 21, to

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brush downwardly therefrom any accumulations of waste materials, so that these materials, ad-

hering to the ledges of the wall member 2D, will not be carried over the top of the closed path followed by the member 20.

A variable-speed transmission |58, having an adjusting means |59, is mounted so that its power output shaft |6| will support a sprocket |62 in alignment with a sprocket |63 fixed to the leftward end of the shaft 35 carrying the sprocket wheels 36. On the rightward end of the shaft 35 a sprocket |64 is mounted, and from this sprocket |64 a chain |65, as shown in Fig. 1, is carried over a sprocket |66 mounted on an idler shaft |61 disposed adjacent the-shaft 18 of the feed roll 11 so that a gear |68, Fig. 2, keyed to the shaft |61 will engage the gear 8| mounted on the rightward end of the shaft 18.

In the operation of the concentrator, the ground ore is fed downwardly from the hopper -1| into the air stream indicated by the arrows 89. The ore particles are carried downwardly through a path, such as indicated by the arrows 9|, and tend to settle toward the upper face of the wall member 20. At the same time, the bellows plate |23 is swinging vertically on the hinge means |22. When the plate |23 moves upwardly, the flap valves |25 thereof are closed, and air is forced upwardly through the screen 2| and the pores of the fabric 22. Accordingly, at this time there is an upward movement of air from the pores of the fabric 22 which tends to resist settling of particles which are being carried downwardly by the flow of air indicated by the arrows 89 and 9|. When the bellows plate 23 moves downwardly, the flap valves |25 open and allow air to enter the chamber |04. The result of this is that there is a very slight suction exerted on the under face of the wall member 29, and accordingly at this time there is essentially no vertical movement of air above the upper surface of the wall member 20. Accordingly, while the bellows plate 23 is moving downwardly, there exists a period of time during which particles of ore above the wall member tend to settle toward the upper surface of the wall member 29. The result of this breathing action is that the lighter particles constituting the ore fed to the concentrator pass down the upper surface of the wall member 20 and are discharged from the lower end thereof as indicated by the arrow |85 of Fig. 5. During the breathing action of air through the wall member 20 and during the feeding of ore thereto, as previously described, the upper or used portion of the wall member 20 is moved at a controlled rate of speed in upward direction due to the driving action of the sprocket wheels 36.

The heavy ore particles, such as metals and chemical compounds of these metals, settle to the surface of the fabric 22. The breathing action is controlled in magnitude, and sometimes in velocity or periodicity, to accomplish the settling of the heavy particles onto the upper surface of the wall member 29 and to cause the light, unwanted ore particles to move down the upper face of the wall member 20 and to be nally discharged therefrom, as indicated by the arrow |85. The heavy ore particles, after they have settled to the surface of the fabric 22, are caused by the breathing action to move downwardly on the surface of the fabric 22 into ore receptacles or pockets |69 formed in the upper faces or forward edges of the riiile bars 23, as shown in Fig. 9. The rile bars 23 are undercut, as shown at |10, so as to produce the concentrate pockets |69, and these concentrate pockets |69 are guarded against breathing of air through the wall member 26 by the edges |1| of the guard strips 26 which project, as shown in Fig. 9, so as to lie under, and project slightly beyond the pockets |69. There is more or less of a small Vertical movement of the wall member 2D and the fabric 22 due to the action of the air movement produced by the reciprocation of the bellows plate |23. This vertical movement or vibration of the wall member 22 iseffectually restrained by the upper and lower guides formed in part by the upper and lower bars 65 and 63 which, as previously described, extend longitudinally or in the direction of movement of the upper extension of the wall member 20 which passes over the chamber |94.

The invention provides means forcontrolling the breathing action through selected parts of the wall member 20. For example, under the feeder 69 the velocity of the air blast, and the turbulence thereof, are relatively strong; therefore, below the wall member 20 at this point laterally elongated butterfly valves |12 are mounted on lateral shafts |13, as shown in Fig. 5. As shown in Fig. 3, the extending leftward ends of the shafts |13 are provided with handles |14 whereby the shafts |13 may be rotated so as to swing the valve members or bailles |12 into such positions as indicated by dotted lines |15 in Fig. 5. After the wall member passes the roller |93, there is no further breathingaction through the wall member 29, and the upper surface of the fabric 22 at this point is essentially quiescent. As previously described relative to Fig. 9, the control plate 94 is adjusted so that air from the blower will be deflected downwardly onto the upper face oi' the wall member v29 to remove light waste materials therefrom. The strength of the air blast delivered by the blower 92 might be controlled by varying the velocity of the impeller |16 thereof, but the simplest manner of producing the desired control of the air blast is through the provision of inlet gates |18 for controlling the entrance of air into the blower 92. In the concentrator disclosedI believe that the ability to obtain high eciency under different conditions of operation is due to the relative adjustability of the different functions of the apparatus. For example, the feeding of ore particles, the blast of air for producing the distribution of ore particles across the upper face of the wall member 29, the velocity of the wall member, and the breathing action produced by the bellows plate |23 may be .z

individually controlled with relation to each other, with the result that the desired ore constituents are collected in the pockets |69 of the riie bars 23, and the waste materials are discharged from the lower end of the device. The concentrates are discharged from the wall member as it travels from the sprocket wheels 36 to the guide wheels 42. It is found that extremely ne metal particles may enter the pores of the fabric 22. Some of these particles pass through the pores of the fabricl 22 during the breathing action exerted when the wall member is above the chamber |94, such particles passing into the chamber |64 and nally being carried down into the collecting pocket |89 formed between the walls and ||2. Other of the minor particles held in the pores of the fabric 22 are released during the movement of the wall member 26 across the sloping plate or wall 93.

I claim as my invention:

1. I'n a conc'entractor of the character described, the combination of: a wall member adapted vto be moved upwardly through .a sloping path of movement, said wall member being formed in a continuous loop and comprising a screen having metal strips secured to the edges thereof, a layer of fine mesh fabric on the upper face of said screen, and lateral riille bars secured to the upper face of said vfabric in longitudinally spaced relation; supporting means for said wall member comprising a sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; sealing members operative between the inner edges of said edge holding means and said metal strips; a feeder for materials to be treated, disposed near the upper end of said sloping frame and above said wall member; means for driving said feeder; means for applying impulses of air to the lower face of said wall member of such strength that air will pass through said wall member; `guide means carried by said sloping frame in positions above and below the intermediate parts of said Wall member disposed between said shoulders of said sloping frame and limiting the vertical movement of said parts of said wall member; and means disposed at the upper end of said sloping frame for producing a downward blast of air under said feeder and downwardly relative to the upper face of said wall member.

2. In a concentrator of the character described, the combination of: a wall member adapted to be moved upwardly through a sloping path of movement, said wall member being formed in a continuous loop and comprising a screen having metal strips secured to the edges thereof, a layer of fine mesh fabric on the upper face of said screen, and lateral riliie bars secured to the upper face of said fabric in longitudinally spaced relation; supporting means for said wall member comprising a sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; a feeder for materials to be treated, disposed near the upper end of said sloping frame and above said wall member; means for driving said feeder; means for applying impulses of air to the lower face of said Wall member of such strength that air will pass through said wall member; and guide means carried by said sloping frame in positions above and below the intermediate parts of said wall member disposed between said shoulders of said sloping frame and limiting the vertical movement of said parts of said wall member.

3. In a concentrator of the character described, the combination of a wall member adapted to be moved upwardly through a sloping path of movement, said wall member being formed in a continuous loop and comprising a screen having metal strips secured to the edges thereof, a layer of fine mesh fabric on the upper face of said screen, and lateral rifile bars secured to the upper face of said fabric in longitudinally spaced relation; supporting means for said wall member comprising a sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; a feeder for materials to be treated, disposed near the upper end of said .sloping frame and above said wall member; means for driving said feeder; means for vapplying impulses of air to the lower face of said w-all member of such strength that air will pass through said wall member; lower guides carried by said sloping frame between said shoulders thereof, said guides being relatively rigid and preventing downward movement of the intermediate parts of said riflie bars; and upper guide means resiliently applied to the upper part of said wall member between said shoulders of said sloping frame for forcing said wall member toward said lower guides.

4. In a concentrator of the character described, the combination of: a wall member adapted to be moved upwardly through a sloping path of movement, said wall member being formed in a con- 1 tinuous loop and comprising a screen having metal strips secured to the edges thereof, a layer of ne mesh fabric on the upper face of said screen, and lateral riie bars secured to the upper face of said fabric in longitudinally spaced relation; supporting means for said wall member comprising a sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; a feeder for materials to be treated, disposed near the upper end of said sloping frame and above said wall member; means for driving said feeder; means for applying impulses of air to the lower face of said wall member of such strength that air will pass through said wall member; lower guides carried by said sloping frame between said shoulders thereof, said guides being relatively rigid and preventing downward movement of the intermediate parts of said riflie bars; hold-down means spaced above said guides in spaced relation to the upper face of said wall member; and spring members operative between said hold-down means and said wall member to hold said wall member downwardly against said guides.

5. In a concentrator of the character described, the combination of: a wall member adapted to be moved upwardly through a sloping path of movement, said wall member being formed in a continuous loop and comprising a screen having metal strips secured to the edges thereof, a layer of ne mesh fabric on the upper face of said screen, and lateral rifile bars secured to the upper face of said fabric in longitudinally spaced relation; supporting means for said wall member comprising a sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; 'a feeder for materials to be treated, disposed near the upper end of said sloping frame and above said wall member; means for driving said feeder; means for applying impulses of air to the lower face of said wall member of such strength that air will pass through said wall member; lower guides carried by said sloping frame between said shoulders thereof, said guides being relatively rigid and preventing downward movement of the intermediate parts of said riflle bars; hold-down means spaced above said guides in spaced relation to the upper face of said Wall member; and upwardly arched leaf spring members having the =ends thereof connected to said riftle'bars, said spring members engaging said hold-down means and operating to force said wall member downwardly against said guides.

. 6. In a concentrator of the character described, the combination of: a Wall member adapted to be moved upwardly through a sloping path of movement, said wall member being formed in a continuous loop and comprising a' screen having metal strips secured to the edges thereof, a layer of fine mesh fabric on the upper face of said screen, and lateral rife bars secured to the upper face of said fabric in longitudinally spaced relation; supporting means for said wall member comprising a4 sloping frame having shoulders on which said edge strips of said wall member may slide; means for moving said wall member upwardly on said frame; edge holding means disposed above said shoulders and resiliently pressing said metal strips against said shoulders; sealing members operative between the inner edges of said edge holding means and said metal strips; a feeder for materials to be treated, disposed near the upper end of said sloping frame and above said Wall member; means for driving said feeder; means for applying impulses of air to the lower face of said Wall member of such strength that air will pass through said wall member; means disposed at the upper end of said sloping frame for producing a downward blast of air under said feeder and downwardly relative to the upper face of said wall member; and an adjustable deflector member associated with said last named means for directing air downwardly against the upper face of said wall member at a point above said feeder.

HAROLD A. ADAMS. 

